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Chapter 22
Descent with Modification |
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three striking observations about life |
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1. the striking ways in which organisms are suited for life in their environment
2.the many shared characteristics (unity) of life
3. the rich diversity of life
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Concluded that life forms could e arranged on a ladder of increasing complexity: "scala naturae" |
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developed the binomial format for naming species |
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layers of rock that essentially house fossils |
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-advocated catastrophism
-inferred that extinctions must have been a common occurrence in the history of life through his examinations of fossils
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the principle that events in the past occurred and were caused by mechanisms different from those operating presently |
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proposed that Earth's geological features could be explained by gradual mechanisms still operating today |
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created the principal of uniformitarianism |
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states that mechanisms of change are constant over time |
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Developed the principles:
-use and disuse: the idea that parts of the body that are used become larger/stronger while those that are not used deteriorate
-inheritance of acquired traits: an organism could pass these modifications to its offspring
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-"On the Origin of Species by Means of Natural Selection"
-natural selection
-adaptations
-descent with modification
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inherited characteristics of organisms that enhance their survival and reproduction in specific environments |
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a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits |
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the modification of species over generations by selecting and breeding individuals that possess desired traits |
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descent with modification |
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characteristics present in an ancestral organism are altered (by natural selection) in its descendants over time as they face different environmental changes |
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similarity resulting from common ancestry |
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structures that represent variations on a structural theme that was present in their common ancestor |
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the independent evolution of similar features in different lineages |
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where species share features because of convergent evolution |
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the geographic distribution of species |
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the slow movement of Earth's continents over time |
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evolution on its smallest scale |
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-wrote about inheritance in pea plants
-proposed a particulate model of inheritance in which organisms transmit discrete heritable units (genes) to their offspring
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differences among individuals in the composition of their geners or other DNA segments. |
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can be classified on an either-or basis. many discrete characters are determined by a single gene locus with different alleles that produce distinct phenotypes. |
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most heritable variation. heritable quantitative variation usually results from the influence of two or more genes on a single phenotypic character |
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the average percentage of loci that are heterozygous |
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differences in the genetic composition of separate populations |
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a graded change in a character along a geographic axis |
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a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring |
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consists of all copies of every type of allele at every locus in all members of the population |
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States that the frequencies of alleles and genotypes in a population will remain constant from generation to generation, as long as it follows HW conditions |
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Conditions for Hardy-Weinberg Equilibrium |
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1. No mutations
2. Random mating
3. No natural selection
4. Large population
5. No gene flow |
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a chance event causing allele frequencies to fluctuate unpredicatbly from one generation to the next (especially in small populations) |
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when a few individuals become isolated from a larger population, & the smaller group establishes their own population, whose gene pool differs from the source population |
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a severe drop in population. by chance alone, certain alleles may be overrepresented among survivors, others underrepresented, or some completely absent. |
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1. significant in small populations
2. can cause allele frequencies to change at random
3. can lead to a loss of genetic variation within populations
4. can cause harmful alleles to become fixed
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the transfer of alleles into or out of population due to the movement of fertile individuals or their gametes |
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the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals |
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occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction or the other. common when a population's environment changes or when members of a population migrate to a new and different habitat. |
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occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes |
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acts against both extreme phenotypes and favors intermediate variants. this mode of selection reduces variation and tends to maintain the status quo for a particular phenotypic character |
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a form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates |
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a difference between the two sexes in secondary sexual characteristics (size, color, behavior, etc) |
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individuals of one sex (usually females) are choosy in selecting their mates of the other sex |
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differences in DNA sequence that do not confer a selective advantage or disadvantage |
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occurs when natural selection maintains two or more forms in a population. |
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individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes |
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frequency-dependent selection |
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the fitness of a phenotype depends on how common it is in the population |
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why natural selection cannot fashion perfect organisms |
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1. selection can act only on existing variations
2. evolution is limited by historical constraints.
3. adaptations are often compromised.
4. chance, natural selection, and the environment interact
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the process by which one species splits into two or more species |
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changes over time in allele frequencies in a population |
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the broad pattern of evolution above the species level |
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biological species concept |
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according to this concept, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
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the existence of biological factors that impede members of two species from interbreeding and producing viable and fertile offspring |
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offspring that result from an interspecific mating |
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block fertalization from occurring |
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may contribute to reproductive isolation after the hybrid zygote is formed |
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two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers
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species that breed during different times of the day, different seasons, or different years cannot mix their gametes. |
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courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species. |
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mating is attempted but morphological differences prevent its successful completion |
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sperm of one species may not be able to fertilize the eggs of another species. |
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the genes of different parent species may interact in ways that impair the hybrid's development or survival in its environment |
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even if hybrids are vigorous, they may be sterile. if the chromosomes of the two parent species differ in number or structure, meiosis in the hybrids may fail to produce normal gametes. since the infertile hybrids cannot produce offspring, genes cannot flow freely. |
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some first-gen hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next gen are feeble or sterile |
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morphological species concept |
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characterizes a species by body shape and other structural features. |
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ecological species concept |
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views a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment |
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phylogenetic species concept |
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defines a species as the smallest group of individuals that share a common ancestor, forming one branch in the tree of life |
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gene flow is interrupted when a population is divided into geographically isolated subpopulations |
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speciation occurs in populations that live in the same geographic area |
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where a species originates from an accident during cell division that results in extra sets of chromosomes |
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is an individual that has more than two chromosome sets that are all derived from a single species |
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a form of polyploidy that results in interbreeding between species |
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a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry |
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reinforcement of reproductive barriers (weak, unfertile, etc offspring) |
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describes a period of apparent stasis punctuated by sudden change. |
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the evolutionary history of a species of group of species |
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a discipline focues on classifying organisms and determining their evolutionary relationships |
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the named taxonomic unit at any level of the heirarchy of the evolutionary tree |
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branch points
(phylogenetic tree) |
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each branch point represents the divergence of two evolutionary lineages from a common ancestor |
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sister taxa
(phylogenetic tree) |
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groups of organisms that share an immediate common ancestor, and hence are each other's closest relatives |
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rooted
(phylogenetic tree) |
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a branch point within the tree represents the most recent common ancestor of all of the taxa in the tree |
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basal taxon
(phylogenetic tree) |
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refers to a lineage that diverges early in the history of a group |
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a branch point from which more than two descendent groups emerge. signifies that evolutionary relationships among the taxa are not yet clear |
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analogous structures that arose independently |
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the discipline that uses date from DNA and other molecules to determine evolutionary relationships |
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each of which includes an ancestral species and all of its descendants |
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- "single tribe"
- a taxon is only equivalent to a clade if it is monophyletic, signifying that it cnsits of an ancestral species and all of its descendants.
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"beside the tribe"
consists of an ancestral species and some, but not all of its descendants |
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"many tribes"
includes taxa with different ancestors |
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shared ancestral character |
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a character that originated in an ancestor of the taxon |
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an evolutionary novelty unique to a clade |
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a species or group of species from an evolutionary lineage that is known to have diverged before the lineage species we study (ingroup) |
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a principle that states we should first investigate the simplest explanation that is consistent with the facts |
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states that given certain probability rules about how DNA sequences change over time, a tree can be found that reflects the most likely sequence of evolutionary events
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are those found in different species, and their divergence traces back to the speciation events that produced the species |
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the homology results from the gene duplication, hence, multiple copies of these genes have diverged from one another within a species |
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much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by natural selection |
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a process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable elements and plasmids, viral infection, and perhaps fusion of organisms |
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a protist that combines photosynthesis and heterotrophic nutrition |
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the process in which certain unicellular organisms engulf other cells, which become endosymbionts and ultimately organelles in the host cell |
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photosynthetic protists
(red and green) |
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red and green algae were ingested in the food vacuoles of heterotrophic eukaryotes and became endosymbionts themselves |
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include some of the most important photosynthetic organisms such as diatoms, and also organisms such as brown algae, and some pathogens |
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protists with membrane bound sacs (alveoli) just under the plasma membrane. |
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protists characterized by cells that are reinforced by cellular plates, with two flagella located in grooves of the protist. include phytoplankton and many other photosynthetic / mixotrophic protists |
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a sexual process in which two individuals exchange haploid micronuclei but do not reproduce |
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protists that include some of the most important photosynthetic organisms.
"hairy" flagellum and "smooth" flagellum |
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unicellular algae that have a glass-like wall made of silicia.
major component of phytoplankton |
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multicellular, most marine
thalli
closest relative to land plants |
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describes an algal body that is plantlike
holdfast, blades, stipe |
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a rootlike anchor that holds algae in place |
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a stem like structure of thallus algae |
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leaflike structures of thallus algae |
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alternation of generations |
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the alternation of multicellular haploid and diploid forms |
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means that the sporophytes and gametophytes are structurally different
(algae) |
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where the sporophytes and gametophytes look similar, but differ in chromosome number.
(algae) |
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extensions that may bulge from almost anywhere on the cell surface |
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most are multicellular, includes the major "seaweeds" |
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structured most like the chloroplasts of land plants, |
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green algae that is most closely related to land plants (more so than chlorophytes) |
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an organism that lives in a symbiotic relationship (mutually beneficial) |
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includes protists that are closely related to fungi and animals |
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organisms that use energy from light to convert carbon dioxide to organic compounds |
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a layer of durable polymer that prevents exposed zygotes from drying out
an adaptation green algae developed to move on land |
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localized regions of cell division at the tips and the roots of shoots that serve as protection |
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multicellular organs that produce spores |
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diploid cells that undergo meiosis and generate the haploid spores inside the sporangia |
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multicellular structures that produce gametes |
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wax and other polymers that cover the epidermis of many species of land plants as a method of waterproofing and preventing dry-out |
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cells joined into tubes that transport water and nutrients throughout the plants body |
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"naked seed" plants
seeds not enclosed in chambers |
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consists of all flowering plants
seeds develop inside ovaries, which mature into fruits/flowers |
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a gamete producing structure |
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liverworts, hornworts, mosses |
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